Hydraulic servo-control



Nov. 14, 1967 R. LUCIEN 3,352,210

HYDRAULIC SERVO-CONTROL Filed Jan. 12, 1965 United States "Patent C) 3,352,210 HYDRAULIC SERVO-CONTROL Rene Lucien, Neuilly-sur-Seine, France, assignor to Recherches Etudes Production R.E.P., Paris, France Filed Jan. 12, 1966, Ser. No. 520,176 Claims priority, application France, Jan. 19, 1965, 2,464 3 Claims. (Cl. 91-434) The present invention has for its object a hydraulic jack of the follow-up control type, operating on a hydraulic station of the so-called closed-centre type.

In hydraulic servo-controls of this type, it is necessary to reduce the internal leakages of liquid to a minimum and, if possible, to eliminate them completely from the interior of the distribution valve.

The servo-control according to the invention fulfills these essential conditions.

It is characterized in that its moving member, actuated by the manual effort to be transmitted by servo-control, is constituted by a cylindrical slide-valve which moves in the interior of a coaxial chamber, the internal faces of which are in contact therewith, the said slide-valve being slidably mounted along its axis on a guiding rod and comprises three transverse channels which pass straight through it, the central channel opening into the interior of the slide-valve in an internal chamber, separated from the other two channels by clapper valves, the seatings of which are formed by the transverse walls of said cham ber, the distribution of the liquid under pressure being effected by the channels under the following conditions:

(a) The central channel terminates in a chamber which is in constant communication with a bore in the abovementioned coaxial chamber and this in turn communicates with the source of fluid under pressure.

(b) The two lateral channels open into two annular grooves in the coaxial chamber and are respectively in communication with one of the jack chambers which they connect alternately to the central chamber of the slidevalve, when the latter is displaced in one direction or in the other to cause the opening of one or the other of the clapper valves.

(c) The slide-valve comprises two annular grooves respectively in communication with the return orifice to the fluid tank, which they put alternatively into communication, depending on the direction of movement of the slide-valve, with the annular groove of the coaxial chamber which is not subjected to the fluid pressure.

Briefly, in the position of rest, the slide-valve closes the supply to the two chambers of the jack, which is thus of the closed-centre type. On the other hand, in this same position, the two chambers are in communication with the return to the tank which is of the open-centre type.

Any movement of the slide-valve from its position of rest simultaneously results, on the one hand in the opening of one or the other of the clappervalves, which causes the fluid under pressure to be supplied to one of the jack chambers, and on the other hand in the closure of the return to the tank of this same chamber.

Other characteristic features and advantages of the follow-u control according to the invention will become apparent from the detailed description which follows below, reference being made to the accompanying drawings given by way of example and without implied limitation.

In these drawings:

FIG. 1 is a longitudinal section of the along the axis of the jack.

FIG. 2 is a transverse section.

In the drawing, 1 refers to the body of the jack and 2 to the piston. It will be assumed that the fixed point of the servo-control is at 3 on the piston rod and that it is the whole of the body 1 which must move in the direction control, taken of the arrows f -f following the action of the manual control which is applied to the cylindrical slide-valve T through the intermediary of the universally-articulated lever 4.

In accordance with the invention, this slide-valve moves in a cylindrical chamber of the body 1, the internal walls of which are in contact therewith, and slides on a guiding rod 5 which passes straight through it along its axis.

The slide-valve is traversed by two channels 6, 7, enclosing a central chamber 8 which communicates by a channel 8a with an annular space 9 formed in the outer portion of the slide-valve. This space is in turn arranged at the level of a conduit 10 with which it is in constan commuincation and which is connected to a source P of fluid under pressure.

Two clapper-valves 11 and 12 having their seatings respectively in the transverse walls of the chamber 8, separate this latter from the channels 6 and 7. The clapper-valves are slidably mounted on the guiding rod 5 and are held against their seatings, in the position of rest of the jack, by a threshold spring 13.

While at rest, each of the lateral channels 6 and 7 opens into an annular groove, 14 and 15 respectively, formed in the body of the jack. The groove 14 is in continuous communication through the intermediary of a conduit 16 with the compartment 17 of the jack, and the groove 15 continuously communicates with the other compartment 19 of the jack, through the intermediary of a conduit 18.

In the position of rest shown in FIG. 1, the grooves 14 and 15 communicate respectively with annular grooves 25) and 21 formed in the slide-valve, which in this same position communicate by means of conduits 22 and 23 with the return orifice 24 to the fluid tank.

The operation of the hydraulic servo-control is as follows:

When the manually-operated lever 4 urges the slidevalve T in the direction of the arrow A, the slide-valve moves and cuts-off the communication between the grooves 15 and 21, of the body and the slide-valve respectively. The clapper-valve 12 comes into contact with the abutment formed by the shoulder 25 of the guiding rod 5. It therefore opens and allows the fluid to pass from the chamber 8 towards the channel 7. The pressure coming from 10 is thus admitted to the compartment 19 of the jack over the path 9-8-7-15-18.

At the same time, the grooves 14 and 20 remain in communication, and the chamber 17 is connected to the return to the tank over the path 1614202224.

The body 1 of the jack thus moves in the direction h under servo-control.

Conversely, when the lever 4 urges the slide-valve T in the direction of the arrow f2, the communication is cut-off between the grooves 14 and 20; the clapper-valve 11 comes into abutment at 26 and is lifted so as to establish communication between the chamber 8 and the channel 6.

The compartment 17 of the jack is thus supplied with fluid under pressure over the path 10-98616 and at the same time the chamber 19 is connected to the return to the tank over the path 18-1521-23-24.

The body 1 of the jack thus moves in the direction f under servo-control.

When the control lever 4 is brought back to its position of rest, the valves 11 or 12, depending on the direction of the force, return to their position on their respective seatings on the slide-valve T and close the supply of fluid under pressure to the compartments of the jack. The two compartments are then in communication with open centre with the return orifice 24 to the tank, through the intermediary of the grooves 14 and 20 and 15 and 21 respectively.

.In order that the operator may feel a restoring eifect proportional to the output force applied to the jack, two annular restoring chambers formed at 27 and 28 comrnunicate respectively with the channels 6 and 7 through the intermediary of conduits 29 and 30 arranged in parallel. The restoring force is supplied for each of the chambers, depending on the direction of movement of the slide-valve, by the pressure acting on the difference of the sections d and d of the extremities of the rod and of the clapper-valvesThe chamber 27 thus creates a restoring force when the pressure is admitted to the chamber 19 and conversely the chamber 28 generates a restoring force when the fluid under pressure is supplied to the chamber 17.

In a similar manner, on the clapper-valves 11 and 12 is applied a force proportional to the difierence of the sections d and d of the outer extremities of the clappervalves and of the central portion of the rod 5.

It is thus possible to pre-regulate the restoring force of the servo-control and the opening of the valves by suitably choosing the sections d d andd of the guiding rod and the clapper-valves.

What I claim is:

1. A hydraulic jack of the follow-up control type operating on a hydraulic station of the so-called closed centre type, said jack comprising a jack body provided with an internal cylindrical chamber, in the interior of said chamber a moving slide-valve in contact with the internal cylindrical walls of said chamber, said slide-valve being slidably mounted on a guiding member fixed to said body and arranged coaxially in the interior of said chamber, said slide-valve being provided with manual operating means and being completely traversed transversely by a central channel and by a first and a second lateral channelarranged on each side of said central channel, said central channel being in constant communication with a bore in said jack body opening into said cylindrical chamber, said bore being connected to a source of fluid under pressure, said slide-valve comprising an internal space into which open said channel and said first and second lateral channels, said cylindrical chamber comprising a first and a second annular grooves in respective communication with a first and a second chambers provided in the interior of the jack body and separated by a plunger piston, said first and second lateral channels opening at the ex: terior of said slide-valve respectively into said first and second annular grooves of said hydraulic chamber, clapper-valves slidably mounted on said guiding member and having as their seatings the transverse walls of said internal space of said slide-valve being provided to put into communication with said internal space either the first lateral channel or the second lateral channel, depending on whether the slide-valve is actuated by said manual control means in one direction or in the opposite direction,- said slide-valve comprising at its periphery a first and a second annular groove in communication respectively with an orifice formed in said jack body for the evacuation of said fiuid under pressure, said first and secondannular grooves of said slide-valve being alternatively in communication, depending on the direction of movement of said slide-valve, with that of said first and second annular grooves of said cylindrical chamber which is not subjected to the fluid pressure.

2. A hydraulic jack as claimed in claim 1, in which said slide-valve further comprises two auxiliary, so-called restoring chambers, said auxiliary chambers being mounted in parallel on the pressure circuits supplying said first and second chambers of said jack body, separated by said plunger piston, each of said auxiliary chambers being formed level with two parts of said guiding member, said parts having transverse sections of difierent areas, so that the operator actuating said manual control means feels a restoring effect proportional to the output force applied to said plunger piston.

3. A hydraulic jack as claimed in claim 1, in which each of said clapper-valves slides atone of its extremities on a first part of said guiding member located in the interior of said internal chamber of said slide-valve, and is guided externally at its other extremity by a recess in said slide-valve, in contact with a second part of said guiding member, said first and second parts having transverse sections of different areas, whereby said clapper valves are subjected to a force applied by the fluid under pressure.

References Cited UNITED STATES PATENTS 2,919,681 1/1960 Schultz ,91434 2,934,089 4/1960 Meyers 91-434 2,985,146 5/1961 Randol 91434 MARTIN P. SCHWADRON, Primary Examiner.

PAUL E. MASLOUSKY, Examiner. 

1. A HYDRAULIC JACK OF THE FOLLOW-UP CONTROL TYPE OPERATING ON A HYDRAULIC STATION OF THE SO-CALLED CLOSED CENTRE TYPE, SAID JACK COMPRISING A JACK BODY PROVIDED WITH AN INTERNAL CYLINDRICAL CHAMBER, IN THE INTERIOR OF SAID CHAMBER A MOVING SLIDE-VALVE IN CONTACT WITH THE INTERNAL CYLINDRICAL WALLS OF SAID CHAMBER, SAID SLIDE-VALVE BEING SLIDABLY MOUNTED ON A GUIDING MEMBER FIXED TO SAID BODY AND ARRANGED COAXIALLY IN THE INTERIOR OF SAID CHAMBER, SAID SLIDE-VALVE BEING PROVIDED WITH MANUAL OPERATING MEANS AND BEING COMPLETELY TRANSVERSED TRANSVERSELY BY A CENTRAL CHANNEL AND BY A FIRST AND A SECOND LATERAL CHANNEL ARRANGED ON EACH SIDE OF SAID CENTRAL CHANNEL, SAID CENTRAL CHANNEL BEING IN CONSTANT COMMUNICATION WITH A BORE IN SAID JACK BODY OPENING INTO SAID CYLINDRICAL CHAMBER, SAID BORE BEING CONNECTED TO A SOURCE OF FLUID UNDER PRESSURE, SAID SLIDE-VALVE COMPRISING AN INTERNAL SPACE INTO WHICH OPEN SAID CHANNEL AND SAID FIRST AND SECOND LATERAL CHANNELS, SAID CYLINDRICAL CHAMBER COMPRISING A FIRST AND A SECOND ANNULAR GROOVES IN RESPECTIVE COMMUNICATION WITH A FIRST AND A SECOND CHAMBERS PROVIDED IN THE INTERIOR OF THE JACK BODY AND SEPARATED BY A PLUNGER PISTON, SAID FIRST AND SECOND LATERAL CHANNELS OPENING AT THE EXTERIOR OF SAID SLIDE-VALVE RESPECTIVELY INTO SAID FIRST AND SECOND ANNULAR GROOVES OF SAID HYDRAULIC CHAMBER, CLAPPER-VALVES SLIDABLY MOUNTED ON SAID GUIDING MEMBER AND HAVING AS THEIR SEATINGS THE TRANSVERSE WALLS OF SAID INTERNAL SPACE OF SAID SLIDE-VALVE BEING PROVIDED TO PUT INTO COMMUNCATION WITH SAID INTERNAL SPACE EITHER THE FIRST LATERAL CHANNEL OR THE SECOND LATERAL CHANNEL, DEPENDING ON WHETHER THE SLIDE-VALVE IS ACTUATED BY SAID MANUAL CONTROL MEANS IN ONE DIRECTION OR IN THE OPPOSITE DIRECTION, SAID SLIDE-VALVE COMPRISING AT ITS PERIPHERY A FIRST AND A SECOND ANNULAR GROOVE IN COMMUNICATION RESPECTIVELY WITH AN ORIFICE FORMED IN SAID JACK BODY FOR THE EVACUATION OF SAID FLUID UNDER PRESSURE, SAID FIRST AND SECOND ANNULAR GROOVES OF SAID SLIDE-VALVE BEING ALTERNATIVELY IN COMMUNICATION, DEPENDING ON THE DIRECTION OF MOVEMENT OF SAID SLIDE-VALVE, WITH THAT OF SAID FIRST AND SECOND ANNULAR GROOVES OF SAID CYLINDRICAL CHAMBER WHICH IS NOT SUBJECTED TO THE FLUID PRESSURE. 